The present invention relates to viewing scopes and, more particularly, to an image focusing ocular piece for such a viewing scope enabling image transmission media which might be damaged due to flexing, such as quartz silica fiberoptic bundles, to be used with many traditionally designed viewing scope probes.
Fiberoptic viewing scopes are now widely used to facilitate the visual checking of an operation or state which otherwise is hidden from view. For example, such scopes are used in the medical field to provide non-invasive views internally of a human body for exploration or during treatment. Fiberoptic viewing scopes utilized in the medical industry typically are known as endoscopes. Viewing scopes also find industrial applications in non-destructive testing, to view the interior of engines or the like, etc. Industrial viewing scopes are generally referred to as borescopes.
A fiberoptic viewing scope most often includes an elongated probe or insertion tube which terminates in a probe head at a distal tip. An image transmission medium, such as a fiberoptic bundle, extends through the probe to the head for transmission of the image to be viewed to an image focusing ocular piece positioned at the exterior of the body or object under investigation. The ocular piece typically includes an eyepiece containing lenses to intercept the image from the transmission medium and focus it for viewing. In some instances, the ocular piece is adapted to be secured to a camera or the like to enable a photograph of the image to be taken.
An illuminating light guide also is often provided as part of a viewing scope, extending from the ocular piece through the probe to the probe head. The purpose of the light guide, generally also a fiberoptic bundle, is to convey illuminating light from the exterior of the body or object being viewed, to the probe head or tip, i.e., the viewing point. Control wires or other elongated elements also commonly extend through a probe outer cover to a probe head. Some viewing scopes even include working channels extending through the probe to permit passage of operating instruments to the distal tip.
Fiberoptic bundles used for image transmission generally are made from glass or plastic strands clad with a material of lower refractive index. While bundles of fiberoptic strands made from such materials are satisfactory for many purposes, they do have some limitations. For example, because of light loss in such standard fiberoptic materials, the length of instruments requiring image transmission with high resolution and discrimination is limited to about three meters.
The art is turning to fiberoptic bundles made from quartz silica fiber strands as image transmission media. The light loss from a quartz silica bundle is significantly smaller than the light loss from the same length of a fiberoptic bundle of glass and/or plastic strands. This results in viewing scopes utilizing quartz silica fiber bundles for image transmission having probes as long as 100 meters to provide effectively the same light transmittance one can obtain from a fiberoptic bundle made from glass and/or plastic having a length of 6 meters. Moreover, quartz silica fibers also are generally resistant to the effects of atomic radiation; are capable of transmitting ultra-violet light (useful in non-destructive testing); can transmit high power/energy laser light; are resistant to heat; and provide excellent color transmission. Unfortunately, one characteristic of quartz silica fiberoptic bundles has limited their wide usage. That is, quartz silica fibers are significantly less flexible than standard glass and plastic fibers. Thus, they are incapable of withstanding relatively small radius bending or flexing without incurring damage. Bending or flexing beyond the quartz silica elastic limit can result in fiber breakage or fracturing and corresponding destruction of the image bundle or, at the minimum, of image clarity. Thus, although manufacturers have incorporated quartz silica fibers in their traditional flexible viewscope designs, they have found that acceptable flexibility has been greatly diminished.